if you look through the sight glass when you are asking the boiler to come on in heating or hot water mode does the pilot light if yes can you hear a continuious click click clicking noise whilst the pilot is lit if so it is the main ignition pc board if there is no flame during this ignition sequence it could be a blocked pilot or the solenoid on the gas valve is not opening to allow gas to the pilot if its dead completely with no pilot listen to see if the fan runs if you dont hear anything it may be the fan or air pressure switch
john patterson, April 2009
